1. Field of the Invention
This invention relates to the use of certain isatin derivatives containing sulfo groups or carboxyl groups for coloring keratin-containing fibers and to coloring formulations containing these isatin derivatives.
Keratin-containing fibers, for example hair, wool or furs, are generally colored either with substantive dyes or with oxidation dyes which are formed by oxidative coupling of one or more primary intermediates with one another or with one or more secondary intermediates. Although intensive colors with good fastness properties can be obtained with oxidation dyes, development of the color takes place under the effect of oxidizing agents, such as H.sub.2 O.sub.2 for example, which frequently results in damage to the fibers. Although substantive dyes are applied under more moderate conditions, their disadvantage is that the colors often have unsatisfactory fastness properties.